The invention relates to a method for emergency unlocking of an automatic transmission of a vehicle.
A device for protecting a vehicle from unauthorized use is known from German patent publication DE 101 22 164 A1, for example. In this patent document, a gear selector lever is locked in a non-operational position when the vehicle is turned off. Driving the vehicle is impossible even with unauthorized startup of the engine, e.g., by short-circuiting the ignition, because the gear selector lever is in a non-operational position. The gear selector lever can be unlocked from this non-operational position only with an ignition key.
In addition, there are known vehicles having an automatic transmission with which the transmission is automatically shifted to the park setting as soon as the engine is shut down, unless the transmission is in neutral and the key or some other identification means is inserted into the ignition lock. Without renewed identification, the transmission cannot be brought to another status or a different mode. If the driver cannot identify himself, e.g., because he has lost his key or identification card or the vehicle is defective, the automatic transmission must be unlocked manually by means of an emergency unlocking unit for towing because otherwise the drive wheels would be locked. If the transmission is unlocked by means of the emergency unlocking unit, the transmission can be switched to any operating modes, including a driving mode.
The object of this invention is to provide a method for emergency unlocking of an automatic transmission which offers improved protection against unauthorized use of the vehicle.
The inventive method for unlocking an automatic transmission of a vehicle from a blocked state for protection against unauthorized use by means of an emergency unlocking unit is characterized in that when the emergency unlocking unit is operated, the automatic transmission cannot be operated in a forward driving mode.
The blocked state of the vehicle is when, for example, no user of the vehicle can be identified and the engine is off. The identification may be accomplished either by inserting a key or some other identification means into the ignition lock or by means of a magnetic card that identifies the driver or a transmission device that need not be connected directly to the vehicle. In general terms, a blocked state should prevail when no use of the vehicle is intended. As long as the vehicle is in a blocked state, the automatic transmission is locked, usually in the park setting and thus it is impossible to shift gears. The automatic transmission can be shifted mechanically by a traditional gear selector lever or electrically by means of a gear selector switch and a control unit. For example, if the vehicle must be towed because of an engine defect and if identification is no longer possible, the automatic transmission can be unlocked by means of the emergency unlocking unit. According to this invention, however, the automatic transmission cannot then be operated in the forward driving mode. Accordingly, the automatic transmission may not be operated in forward driving mode even when the gear is shifted to a manually switchable mode. The advantage is that an unauthorized user of the vehicle who might indeed start the vehicle without identification means cannot nevertheless drive it away even if he operates the emergency unlocking unit.
Operation of the automatic transmission in the forward driving mode may advantageously be prevented by mechanical or electrical means, whereby the advantage of preventing this action electrically is that there need not be any additional mechanical blocking device in the vehicle.
Operation of the automatic transmission in the forward driving position can advantageously be prevented by the fact that a gear selector lever which is provided in the vehicle cannot be moved into the forward driving position on activation of the emergency unlocking unit. The gear selector lever can be prevented by means of a mechanical blocking device from being moved into the forward driving position, for example. If the gear selector lever cannot be moved into the forward driving position, the control unit triggering the electrohydraulic valves of the automatic transmission cannot receive a forward driving signal from the gear selector lever and accordingly it cannot send the automatic transmission a triggering signal for operation of the automatic transmission in forward driving mode.
In another possible embodiment, operation of the automatic transmission in the forward driving mode can also be prevented by the fact that advantageously the control unit present in the vehicle cannot send a signal for operation of the automatic transmission in a forward driving mode on operation of the emergency unlocking unit for selecting a driving mode and/or for triggering the electrohydraulic valves of the automatic transmission. If the control unit were to receive an input signal for operation of the automatic transmission in the forward driving mode from the gear selector lever, then according to this possible embodiment, it would not trigger the electrohydraulic valves of the automatic transmission. The control unit then could not perform any triggering of the automatic transmission at all, for example, or it could perform such triggering as if it had received an input signal for operation of the automatic transmission from the gear selector lever in parking mode or in neutral mode.
On operation of the emergency unlocking unit, the automatic transmission advantageously also cannot be operated in a reverse driving mode. However, this advantageous embodiment is possible only with electric blocking via the control unit because in mechanical blocking of the gear selector lever, no shifting at all would be possible because in the gear selector unit, the reverse driving position is situated between the park setting and the neutral position. Then the transmission could also no longer be operated in the neutral mode, as is required in towing operation.
The emergency unlocking unit may advantageously be operated via a locking cylinder. Such requirements are stipulated in various countries to provide additional protection against unauthorized emergency unlocking.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.